The invention relates to a device for cleaning a cylinder in a printing machine, the cylinder having a jacket surface with at least one raised element, particularly at least one gripper for gripping a sheet of printing material, the cleaning device having a cleaner engageable with the jacket surface of the cylinder and being rotatable about an axis of rotation for cleaning the jacket surface.
Impression cylinders and sheet transfer drums installed in printing machines carry grippers which project beyond the periphery of the cylinder. The rotating cylinders are cleaned by cleaners in the form of cleaning rollers, cloths or brushes which can be brought into contact with the cylinders. In order to avoid damage to the cleaner by the grippers, precautions have to be taken.
The published German Utility Model Document DE 295 16 979 U1 describes a washing device for cleaning cylinders of an offset printing unit. The cylinders to be cleaned carry elevated grippers, and the cleaner is formed as a washing roller that rotates during cleaning. A control device is provided, by which the washing roller can be lifted away over rows of the grippers. With this washing device as the cleaner, it is possible to perform a more effective cleaning of the cylinder than with a cleaner in the form of a cloth. The rotation of the washing roller produces an increase in the relative movement between the surface to be cleaned and the cleaner. However, a lifting device is needed in order to lift the washing rollers over and beyond the rows of grippers, and thus a high outlay in terms of construction and control is necessary. The washing roller that is installed is not formed as a brush roller. The cleaning action is therefore lower, than with cleaners provided with brushes. Washing liquid which is sprayed on the washing roller is doctored off the latter by a wiper.
Furthermore, Japanese Patent 3-75348 describes a device for washing impression cylinders of an offset printing machine, in which the cleaner is in the form of a cloth which is pressable against the cylinders by two pressure plates. The pressure plates are formed with recesses which correspond to the grippers. One of the pressure plates is constructed so as to be laterally displaceable. The displacement of the one pressure plate occurs before it strikes the gripper and as a function of or in accordance with a signal transmitted by a detector that detects the grippers. The lateral displacement takes place alternately in two directions in order to compensate for the cloth slipping to one side on the pressure plates. Although the cleaner can be held in a position wherein it is in permanent or continuous contact with the rotating cylinder during the cleaning operation, effective cleaning of the cylinder is not possible with this device, because the relative movement between the cloth, which does not rotate during the cleaning operation, and the cylinder is produced only by the rotation of the cylinder. The cloth is not suitable for various types of soiling and surface structures of cylinders, in particular for removing paper particles stuck to a rough cylinder jacket surface. With this cloth pressed against the cylinder, the cleaning takes a comparatively long time in many cases, because the scouring action is low. Because the cloth does not have any cutout or recess through which the grippers can pass, it unavoidably becomes severely deformed, which reduces the cleaning quality.
It is accordingly an object of the invention to provide a device for cleaning a cylinder with a raised or elevated element in a printing machine, which is compact and of simple construction.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a device for cleaning a cylinder in a printing machine, the cylinder having a jacket surface with at least one raised element, the cleaning device comprising a cleaner engageable with the jacket surface of the cylinder and being rotatable about an axis of rotation for cleaning the jacket surface, the cleaner being formed with at least one recess through which the at least one raised element is able to pass.
In accordance with another feature of the invention, the cleaner is formed as a roller.
In accordance with a further feature of the invention, the roller is a brush roller.
In accordance with an added feature of the invention, the at least one recess extends in a circumferential direction of the cleaner over a circumferential angle less than 360xc2x0.
In accordance with an additional feature of the invention, the cleaner is formed as a roller, and the at least one recess is a single flat formed on the roller.
In accordance with yet another feature of the invention, the cleaning device includes a rotary drive for rotating the cleaner to match the rotation of the cylinder so that the at least one raised element passes contact-freely through the at least one recess.
In accordance with yet a further feature of the invention, the cleaning device includes a rotary drive for rotating the cleaner to match the rotation of the cylinder so that the at least one raised element passes without hindrance through the at least one recess.
In accordance with yet an added feature of the invention, the cleaner is nonuniformly rotatable while the at least one raised element passes through the at least one recess.
In accordance with yet an additional feature of the invention, the rotation of the cleaner is delayable while the at least one raised element is passable through the at least one recess.
In accordance with still another feature of the invention, the cleaning device includes a plurality of recesses extending in circumferential direction of the cleaner.
In accordance with still a further feature of the invention, the cleaner is formed as a roller, and each of the recesses is formed by an annular groove on the roller.
In accordance with still an added feature of the invention, the recesses extend in the circumferential direction of the cleaner over a circumferential angle of 360xc2x0.
In accordance with still an additional feature of the invention, the cleaning device includes an oscillatory drive for oscillating the cleaner parallel to the jacket surface of the cylinder
In accordance with another feature of the invention, the cleaner is oscillatable axially by the oscillatory drive so that the raised element is passable through the recess without hindrance.
In accordance with a further feature of the invention, the cleaner is nonuniformly oscillatable.
In accordance with an added feature of the invention, the oscillations of the cleaner are delayable while the raised element is passable through the recess.
In accordance with an additional feature of the invention, the cleaning device includes at least one of a gear mechanism and an electronic control for matching the rotation of the cleaner to the rotation of the cylinder.
In accordance with yet another feature of the invention, the cleaning device includes at least one of a gear mechanism and an electronic control for matching the oscillations of the cleaner to the rotation of the cylinder.
In accordance with another aspect of the invention, there is provided a printing machine in combination with at least one cleaning device as defined hereinabove.
During the cleaning process, the cleaner can remain permanently or continuously in a position wherein it is in contact with the cylinder. This is achieved by shaping the cleaner so that it is matched to the elevated element or elements, each elevated element being assigned at least one recess corresponding thereto on the cleaner.
The cylinder may be a cylinder which carries a sheet of printing material in a gripper, which preferably forms the elevated element. A further type of elevation is represented by tools arranged on the cylinder jacket surface, for example stamping or cutting tools for processing the printing material in line in the printing machine. The cylinder may carry a number of elevated elements arranged in a row parallel to the axis of the cylinder, for example grippers forming a row of grippers. In this case, one recess may be assigned to a number of elevated elements which pass through this recess, or each recess may be assigned to a single elevated element.
The term recess is to be understood as, for example, a narrowed section, a channel, a flat, a depression or hollow, a bore, an eccentric or sickle-shaped turned section or a groove. In the case of a cleaning roller, the raised or elevated element or elements can enter the recess or recesses when the cleaning roller is rolling on the cylinder jacket surface. In the case of a cleaner that is formed as a roller, recesses shaped like segments of a circle or sectors of a circle, as viewed in the direction of the axis of the roller, may be provided. A brush roller may have, for example, four segment-like flats on the outer surface thereof, and a rectangular cross section. The cleaner may also have two cutouts shaped like sectors of a circle and, as viewed in the axial direction, may have the shape of a double brush.
The kinematics and geometry of the cleaner are preferably matched to the elevated elements so that the latter pass through the cleaner without contact by moving through or past the recess. Furthermore, in specific cases, provision may be made for the elevated elements to pass through the recess while making contact with the cleaner.
The cleaner may be formed as a roller or as a rotating brush. A cleaner that is formed as a roller may be covered with a fleece or may preferably be formed as a brush roller filled or studded with bristles. The cleaning action of a rotating cleaner filled with bristles is higher by comparison with devices of the aforementioned prior art. The roller may rotate in the same direction as the cylinder, giving, at the point of contact, an opposite relative movement of the roller outer surface or of the bristles in relation to the cylinder jacket surface, and a very good cleaning action. During the cleaning operation, the roller may rotate at a roller circumferential speed which is different from, in particular higher than, the cylinder circumferential speed. In this case, it is also possible for the roller and the cylinder to rotate in opposite directions.
The recess may extend in the circumferential direction or in the direction of rotation of the cleaner over a circumferential angle of 360xc2x0 or more. A screw-like or helical recess extends over 360xc2x0 or even more. However, a recess that extends over 360xc2x0 is preferably formed as a self-contained annular groove. This construction is advantageous, in particular with regard to the rotary drive of the cleaning roller, which rotates continuously in this construction. To a row of elevated elements, for example the row of grippers, there may be assigned a number of annular grooves arranged so that they are offset in the direction of the cleaner axis.
The recess may extend over a circumferential angle of less than 360xc2x0. Such a recess is preferably formed as a flat that extends essentially over the entire width of a roller-like cleaner. This flat may extend over a number of elevated elements assigned to the recess, for example over all the grippers of a row of grippers. In this case, the outer surfaces close to the ends of the cleaning roller may form supporting regions which are not cut out.
A development of the cleaning device according to the invention may include the cleaner, in particular the cleaning roller, which is rotatable by a rotary drive to match the rotation of the cylinder so that the elevated element passes through the region of the recess without contacting the cleaner or with slight contact which does not damage the cleaner.
A further embodiment may include a control and/or gear mechanisms for ensuring a phase angle of a rotatable cleaner in relation to the phase angle of the rotating cylinder that the elevated element or elements can pass through the recess or recesses without hindrance. For example, the cleaner rotation that is driven by the rotary drive may take place nonuniformly and be suspended, in particular by delaying or retarding the rotation to the value zero, so that the cleaner is at a standstill when the elevated element passes through or past the recess. In addition to the described delay or retardation down to a standstill, i.e., a discontinuous rotation, a cleaner rotation at a nonuniform speed may also be provided in the form of an intermittent slow-down, so that by comparison with a uniform rotation there remains more time for the elevated element to pass through the recess, and the driving takes place particularly smoothly. Braking the cleaner rotation is advantageous, particularly in the case of a roller-like cleaner which has a single flat that is assigned to a number of elevated elements arranged in rows, for example the grippers.
According to a further development, the cleaner may be moved in a reciprocating manner parallel to the outer surface of the cylinder by a cleaner reciprocating drive. The cleaner reciprocating drive can be the drive to the printing machine, which displaces the cleaner laterally to and fro via a cleaner reciprocating mechanism. However, the cleaner may also have an oscillatory drive, for example an electric motor, assigned thereto, the electric motor being independent of the printing machine drive and being also capable of driving the cleaner via a cleaner reciprocating mechanism. The cleaner reciprocating drives and mechanisms which are used may be conventional distributor roller driving systems from inking units of printing machines, for example slider crank mechanisms and eccentric drives.
The lateral cleaner movement is periodic and corresponds in particular to a harmonic oscillation, for example to a sine or cosine function of the reciprocating travel as a function of the cylinder rotation. The cleaner, which constitutes a linear oscillator, oscillates to and fro between the two outer reversal locations, the speed decreasing as the reversal locations are approached. On this basis, one embodiment may provide for the elevated element or the elevated elements, during these movement phases close to or at the reversal locations, to pass through the recess or the recesses, in particular at least one recess shaped like an annular groove. The cleaner reaches the maximum speed in the central position, at an elongation with the value 0. In particular applications, it is beneficial for the elevated element to pass through the recess, for example the annular groove, precisely during this movement phase or in a movement phase remote from the reversal location. For these cases, provision may be made for the speed of the cleaner reciprocating movement to be reduced while the elevated element or elements pass through the recess or the recesses, it being possible for the cleaner reciprocating movement to be delayed or retarded down to a standstill. Following this stop or retardation, the cleaner is accelerated again. The movement function which results from the delay or retardation corresponds to a nonharmonic oscillation or nonuniform oscillation. In the case of a stop, there is also a discontinuous oscillation.
The device according to the invention can be used in rotary printing machines and, in particular, in sheet-fed rotary printing machines. Furthermore, the device can be used in machines which process printing material.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for cleaning a cylinder in a printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: